Class: Libsvm::Problem

Inherits:
Object
  • Object
show all
Defined in:
lib/libsvm/problem.rb,
ext/libsvm/libsvm.c

Overview

Represents a training set (alternatively called ‘problem’).

In contains labels and examples in equal number.

This class represents the struct svm_problem.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#l ⇒ Integer (readonly)

The number of labels and examples in this traning set. (The name is lowercase-L.)

Returns:

  • (Integer) 



# File 'lib/libsvm/problem.rb', line 13

Instance Method Details

#examples ⇒ [Array<Float>, Array<Array<Node>>]

Returns the array of labels and the array of corresponding examples contained in this training set.

labels, array_of_examples = problem.examples

Returns:



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# File 'ext/libsvm/libsvm.c', line 179

static VALUE cProblem_examples(VALUE problem) {
  struct svm_problem *prob;
  struct svm_node *node, *node_copy;
  double label;
  struct svm_node *features;
  VALUE labels_ary, examples_ary, example_ary, v_node, result;
  int i;

  Data_Get_Struct(problem, struct svm_problem, prob);

  labels_ary = rb_ary_new2(prob->l);
  examples_ary = rb_ary_new2(prob->l);

  features = calloc(prob->l, sizeof(struct svm_node));
  if(features == 0) {
    rb_raise(rb_eNoMemError, "on allocating Libsvm::Node" " %s:%i", __FILE__,__LINE__);
  }

  for(i = 0; i < prob->l; ++i) {
    label = *(prob->y+i);
    rb_ary_push(labels_ary,rb_float_new(label));

    node = *(prob->x+i); /* example start pointer */
    example_ary = rb_ary_new();
    while(node->index != -1) {
      node_copy = malloc(sizeof(struct svm_node));
      if(node_copy == 0) {
	rb_raise(rb_eNoMemError, "on allocating Libsvm::Node" " %s:%i", __FILE__,__LINE__);
      }
      memcpy(node_copy,node,sizeof(struct svm_node));
      v_node = Data_Wrap_Struct(cNode,0,node_free,node_copy);
      rb_ary_push(example_ary,v_node);
      ++node;
    }
    rb_ary_push(examples_ary,example_ary);
  }

  result = rb_ary_new2(2);
  rb_ary_push(result,labels_ary);
  rb_ary_push(result,examples_ary);

  return result;
}

#set_examples(labels, examples_array) ⇒ Integer

Sets the examples and their label for a training set.

The indices of the arrays are supposed to correspond. If they don’t match in length an ArgumentError is raised.

Returns:

  • (Integer) —

    number of examples in the traning set



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# File 'ext/libsvm/libsvm.c', line 132

static VALUE cProblem_examples_set(VALUE obj,VALUE labels_ary,VALUE examples_ary)
{
  struct svm_problem *prob;
  int i;

  int num = rx_ary_size(labels_ary);

  if(num != rx_ary_size(examples_ary)) {
    rb_raise(rb_eArgError, "Number of labels (%i) does not match number of features (%i).", num, rx_ary_size(examples_ary));
  }

  Data_Get_Struct(obj, struct svm_problem, prob);

  if(prob->l > 0) {
    free(prob->y);
    for(i = 0; i < num; ++i) {
      free(*(prob->x+i));
    }
    free(prob->x);
  }

  prob->y = calloc(num,sizeof(double));
  if(prob->y == 0) {
    rb_raise(rb_eNoMemError, "%s:%i", __FILE__,__LINE__);
  }

  for(i = 0; i < num; ++i) {
    *(prob->y+i) =  NUM2DBL(rb_ary_entry(labels_ary,i));
  }

  prob->x = examples_ary_to_internal(examples_ary);
  prob->l = num;

  return INT2FIX(num);
}